Pipes are often installed underground or in areas where access can be difficult. Even though a pipe installation may last for many years, it is sometimes necessary to repair the pipe installation due many factors, such as earthquakes, corrosion, impact, tree root damage, or leakage. In certain cases, the defective pipe can be repaired by lining it with a durable pipe-liner, hereinafter referred to as a liner, thus prolonging the life of the installation by many years; however, installing the liner can be difficult due to the limited availability for sufficient access.
The liner may comprise a combination of materials, construction and method of use such that it is flexible whilst being inserted and becomes rigid or may be caused to become rigid after being positioned in the pipe being lined. A common type of liner is a cured-in-place pipe (CIPP) liner comprising a tube of felt or other flexible absorbent material enclosed in a flexible and substantially impermeable plastic skin, such as polyvinyl chloride or polyurethane, and impregnated with a liquid material, such as resin, that hardens or may be caused to harden following insertion of the liner into the pipe.
One method for inserting a liner is to evert (e.g. turn inside out) it into position within a pipe, so that it turns inside-out and what was previously the external surface forms the inner surface of the liner. Eversion is usually achieved by positioning the end of the liner so that it passes through a nozzle and is turned back over and fastened in place around the nozzle so that, when fluid such as air or water is introduced under pressure through the nozzle, the liner may be caused to turn inside out or evert so that it is drawn through and extends progressively beyond the nozzle. The everting end of the liner may be inserted in the end of a pipe and the continuing application of fluid under pressure causes the liner to evert and extend into the pipe. The nozzle is usually incorporated into a chamber that may be pressurized with a pressurizing fluid or into the end of a vertical tube that may be filled with a liquid, such as water, and the liner is partly or wholly contained within the chamber or tube prior to eversion. Once the liner is fully inserted, it is held in position either by maintaining pressure within it, which requires a provision for the distal end of the liner to be closed to retain the pressurizing fluid, or by means of a length of pressurizable tubing, commonly called an inversion hose, which may be inserted at the same time as the liner or separately everted into the liner after the liner has been put into position in the pipe.
An example of a liner is shown in FIGS. 1 and 2. FIG. 1 depicts the end of a liner in “lay-flat” mode as it exists before being everted. An impervious surface, hereinafter referred to as the skin, forms the exterior of the liner and the body material forms the bulk of the liner. FIG. 2 shows a liner that has been everted through and has emerged out of a pipe. The skin of the liner now forms the inner surface of the liner and the body material forms the exposed exterior of the liner and is in contact with the inner surface of the pipe.
A pressurizable chamber used for everting a liner is called an inversion-drum and may comprise a reel on which the liner is mounted, enclosed within a pressurizable chamber fitted with an outlet nozzle. In alternative embodiments, the pressurizable chamber may be loaded by stuffing or folding the liner, wholly or partly therein, and then closed with a substantially air-tight closure. In all types of pressurizable chambers, the end of the liner passes through the nozzle to the outside of the pressurizable chamber and is everted and fastened round the nozzle with a firm air-tight fastening. When compressed air is applied to the pressurizable chamber, the liner is forced to evert progressively and extend out of the pressurizable chamber and the everting end may be directed into the pipe being lined.
Common inversion-drums are bulky and expensive and may require two or more people to handle them. Smaller versions are available, but their use is limited to shorter liners and they are also fairly expensive, as is a liner-gun comprising a chamber into which a liner may be wholly or partly stuffed and then closed, sealed and pressurized. Some users construct their own pressurizable chambers out of a length of tube fitted with a nozzle at one end and closed at the other, but these can be difficult to load.
When a liner is being everted from an inversion drum at ground level into a drain that runs horizontally underground, part of the section of liner between the inversion drum and the drain usually has to take the form of at least one bend or curve and the nature of the material and construction of the liner usually causes creasing and constriction that hinder the movement of the uneverted part of the liner through the said section of liner between the inversion drum and the drain.
There are also disadvantages with the method of everting a liner by means of a vertical tube filled with water. First, the necessary water supply may not always be readily available. Second, it is often necessary to erect a scaffold platform to support a vertical pipe long enough to deliver the pressure required to drive a liner into a pipe. Third, if the pipe being lined slopes significantly upwards from the point of access, water pressure is progressively reduced at the everting end of the liner as it extends, and if the piper slopes significantly downwards, the weight of water can be too great for the installer or the lining material itself to support. And, fourth, if the eversion process is held up for any reason, it is not possible to raise the operating pressure as a way to get the liner moving again.
There are further difficulties and shortcomings that are common to all of these conventional methods for inserting liners into drains. In the first instance, an everted liner must extend from the point of access to the pipe being lined and cannot be caused to start at a chosen point within a pipe such as beyond a junction where two pipes join. It is possible to make a short localized repairs of up to approximately 2 meters in length, by means of a glass-fiber and resin patch which is wrapped round a semi-rigid bladder called a packer and dragged or pushed into position within a pipe where the packer is pressurized to press and form the patch against the inner surface of the pipe and is then deflated and withdrawn when the resin is cured. However, if the defect is longer than 2 meters or so, several separate patches must be applied or, if a liner is used, holes must be cut in it, both of which increase time and cost. Second, part of the cured liner will always project out of the access end of the pipe being lined and any excess must be trimmed and spillage and contamination must be removed. Third, existing methods for pressurizing an everted liner can involve difficulty and cost. It can be pressurized by closing it at the distal end by, for example, binding it or applying a stopper, but this method can only be used on manhole-to-manhole liners and the end section must be trimmed and the manhole must be made good when the job is finished. Alternatively, a length of inversion hose may be everted simultaneously with the liner, which is a complicated task requiring the operator to thread the liner into the tube beforehand, or it may be dragged in by the liner as it everts which, again, can be complicated or unreliable using existing methods, or it may be inserted into the liner after the liner has been positioned within the pipe being lined, which usually requires that the inversion hose is separately everted into the liner.
An alternative to inverting a liner into a pipe is to drag or push the liner into place and then to pressurize it with a separate pressurizable tube which is usually everted into the liner after the liner has been dragged into place. This can overcome some of the problems associated with conventional eversion methods, but it carries the major disadvantage that the liner cannot be caused to adhere to the inner surface of the pipe and consequently water or other fluid can enter between the pipe and the liner. Grouting the ends of the liner against the pipe can prevent fluid getting into the drainage system provided that the liner runs uninterrupted between two access manholes, but if access to the liner is from one manhole only, a separate patch will be required over the distal end, thus adding cost and reducing the diameter of the repaired pipe. Also, it can be difficult and often impossible to install a standards-compliant liner at locations where pipes branch or converge.
The present invention features a pipe-liner system for use when lining a pipe interior for repair. The present invention provides a substantial improvement in the field of pipe repair by successfully addressing the difficulty with accessing and repairing a damaged pipe.
Any feature or combination of features described herein are included within the scope of the present invention provided that the features included in any such combination are not mutually inconsistent as will be apparent from the context, this specification, and the knowledge of one of ordinary skill in the art. Additional advantages and aspects of the present invention are apparent in the following detailed description and claims.